Electrical issue in microwave box

[ajbrown]

I know from years of reading TOTV there are come electricians lurking here. I was hoping for some tips on how they may debug the root issue.

I am not an electrician by trade, but know my way around general wiring issues. I am not looking for numbers for electricians you have used. I have those if the need be :D

The other day, microwave had no power. First time ever and I have been here since 2007. I went out to garage and found a breaker had kicked. I reset breaker and all seemed fine. A few days later I was using it and saw it power off. I 'think' I heard a pop as it did (this 'pop' may have occurred first time), sure enough breaker had tripped again.

This time I turned breaker OFF and was going to unplug and try microwave in a different outlet to further isolate issue. I had a hard time unplugging. I had to pry it off with a screw driver. The pictures explain why it would not come off.

Looking at the pictures, any explanations come to mind or next steps to further isolate? Thanks for any insight...

http://i1002.photobucket.com/albums/af146/ajbrown2007/totv/20150518_163315_zpskq2iog80.jpg (http://s1002.photobucket.com/user/ajbrown2007/media/totv/20150518_163315_zpskq2iog80.jpg.html)

http://i1002.photobucket.com/albums/af146/ajbrown2007/totv/20150518_163340_zpskdrivfk6.jpg (http://s1002.photobucket.com/user/ajbrown2007/media/totv/20150518_163340_zpskdrivfk6.jpg.html)

PS. My wife swears she has not been using an liquids in that cabinet lately. My initial thought was dirt, or something that got into plug...

[villagetinker]

The "other day" when you first noticed the MW not working and the breaker tripped, was there a storm in the area? This looks like this could be the result of a nearby lightning strike. If not, then the other possibility would be a loose connection in the plug/socket connection. This damage could be overheating due to a loose connection. The heat from the loose connection could easily cause the plug or cord to the MW to fail, and cause a short circuit causing the breaker to trip. If this is the case, replacing the receptacle will only fix half of the problem, as the cord set is probably damaged, and is now probably a fire hazard. I would suggest replacing the MW.

I looked at the photos again, and I see burn marks INSIDE the box next to the receptacle, this looks suspicious to me. Was anything else tripped at this time?

Look very closely at the receptacle when you replace it for burn marks, especially outside the receptacle. If you find these or anything that indicates arcing, please have a licensed electrician check the entire wiring system for possible damage.

Please proceed very carefully here, and I will strongly suggest you get expert help from a licensed electrical contractor. You do have a problem that if not fixed correctly may cause a future fire.
Hope this helps.

[rjm1cc]

Not an electrician but you could have had a lose wire. Buy a new outlet and connect. Be sure screws are tight.

Did microwave work on a different outlet?

If it did I would plug back into the new outlet.But for a while I would unplug it when not using.

Fire is a big risk.

[ajbrown]

villagetinker, Thanks, it does make sense.To be clear, there will be no chances taken...

Nothing else is tripped. The microwave is on an isolated circuit. I suspect the 'plug' and the receptacle are NG now. Further examination is required.

I can certainly explain such a thing by a loose connection or a dirty connection, but...

Is it possible that a microwave can ask for so much power that it overheats the components before a circuit trips? This is a pretty bad design, no? No wiring changes have occurred in this home.

I ponder if there is any harm in testing the microwave off of a similar sized circuit, but using a GFI outlet for more protection. How does one prove a microwave is ok?

[ajbrown]

Not an electrician but you could have had a lose wire. Buy a new outlet and connect. Be sure screws are tight.

Did microwave work on a different outlet?

If it did I would plug back into the new outlet.But for a while I would unplug it when not using.

Fire is a big risk.

Thank you. My next step is to pull the receptacle out of the box and inspect the connections a bit later.

[ajbrown]

Much worse that I could have expected. Going to call warranty (or someone in TV) to see what resources they can provide to understand root issue. This is more than a switch that does not work. I cannot ever remember seeing something like this before, but maybe I have been lucky in my previous homes...

The black wire (burned) may have come disconnected when I pulled receptacle out of box. It does seem all of the wires have a good tight connection.

I am taking no further action at this time. A piece of duct tape is over the breaker to prevent accidental turn on.

http://i1002.photobucket.com/albums/af146/ajbrown2007/totv/20150518_175750_zpshayhxx5t.jpg (http://s1002.photobucket.com/user/ajbrown2007/media/totv/20150518_175750_zpshayhxx5t.jpg.html)

[Uberschaf]

Black wire (load) was loose on receptacle causing heat issue.New plug,new receptacle and your good to go.I believe your microwave is 1800 watts which is 15 amperes and the receptacle is a 20 amp. Loose wire.

[villagetinker]

To all,
Many of the original receptacles and switches use PUSH IN WIRE CONNECTIONS. Personally I do not like these. My step son moved into a mobile home recently, and in the process of adding a GFCI to bring it up to code, some of the wires in other receptacles on the same circuit pulled out of the receptacles as I was taking these out of the box, YIKES!!. I immediately replaced every switch and receptacle, and use the screw terminals.

A follow up discussion with UL indicated the specific brand (about 20 years old) was recalled and delisted due to problems with the push in connections, and the newer versions were redesigned to avoid these problems. IMHO, I still like the properly torqued screw connections.

I would hope some of the electrical inspectors jump in here.....

ALL, please do not attempt electrical repair, unless you really know what you are doing, plastic boxes are not going to contain a fire, and while the push in connectors are typically use, it is interesting that there appear to be more then one instance of problems. I will be inspecting ours tomorrow.

AJBrown, I would bet the black wire was nicked and stressed to the point of almost breaking, then repeated used (aka heating and cooling) caused the failure, this is just a guess.

Also, you could take the microwave to the garage, there is a dedicated 20 amp GFCI circuit, or use one of the counter outlets (15 amp GFCI) in the kitchen. MAKE SURE YOU HAVE A CUP OF WATER OR EQUAL IN THE MICROWAVE. But I would have the cord set carefully inspected for damage, and replaced if possible.

[DonH57]

Black wire (load) was loose on receptacle causing heat issue.New plug,new receptacle and your good to go.I believe your microwave is 1800 watts which is 15 amperes and the receptacle is a 20 amp. Loose wire.

I'm thinking that too as any loose connection of a wire and a device or a two wire connection will cause excessive heat melting components causing damage.

[l2ridehd]

The Villages electricians use the type receptacle where you strip and push the wire in a hole. Over time and a heavy load (microwave) these connections will arc. Very minor at first, but over time will cause the exact problem you have. I would strip the 12-2 Romex back a few inches if possible, replace the outlet with a new one, use the screws on the side vs the push in holes, replace the plug on the microwave cord, and you should be good to go. Might also check the screw on the breaker to be sure that is tight as well. Somewhere in the circuit there was a loose connection. Most likely the connection at the outlet, but would also check the CB in the panel.

If you need any assistance just PM me and I will come over and give you a hand.

[l2ridehd]

Looking at the photo more closely, looks like the did use the screw on the side of the outlet. Could have been loose, could have been scored by wire strippers when installed, could have been cut covering and arced to the ground wire, but this was most likely an issue when installed. Replace all the components, make sure all connections are tight and you should be fine.

[ajbrown]

Thanks all. Everything you have posted makes good sense and was the feed back I was hoping for. I also appreciate the multiple offers for assistance. In this case I will be all set, but thank you, it is very nice :clap2:

I am feeling better that the microwave is not the culprit and will test it on a GFI circuit. Facts as we know them lean towards this issue existing since the installation of the wiring when the house was built.

It does make me ponder how many other 'sleeping time bombs' exist :popcorn:.

[ajbrown]

A couple of interesting pictures... I mean, I think they are interesting :blahblahblah:


If you look close you can see what looks like a hole through the body of the receptacle. The wire no longer comes out the normal path.

It is unclear if the hole goes through. I do not wish to change "the evidence" to find out if it does. I may give the fire dept. a call to see if they can take a look. Why not.. I am a curious guy...

http://i1002.photobucket.com/albums/af146/ajbrown2007/totv/be49dc57-b9ef-4e68-83b0-05ec32e20e2a_zpswefnvauc.jpg (http://s1002.photobucket.com/user/ajbrown2007/media/totv/be49dc57-b9ef-4e68-83b0-05ec32e20e2a_zpswefnvauc.jpg.html)

Here is the other side of "what appears to be" a hole.

http://i1002.photobucket.com/albums/af146/ajbrown2007/totv/20150519_080655_zps5svwrf2t.jpg (http://s1002.photobucket.com/user/ajbrown2007/media/totv/20150519_080655_zps5svwrf2t.jpg.html)

[TimH25]

Could you say how you are getting on please.

[villagetinker]

Yes, I was wondering also if AJBrown found the root cause of the problem.

[ajbrown]

All has been fine since the last day I posted. I ran the micro wave off another outlet for dinner and had no issues, so after the things I read here and online, I concluded the issue was the original installation by the person who wired that outlet or possibly the receptacle.

I replaced the receptacle and the plug and all has been fine.The first couple of days I even would go up and feel the plug for any heat but there is none.

thanks again!!

PS. I do keep an eye on it, just not as often as after installation

[villagetinker]

Thanks for the update, I have checked ours also, so far no indication for problems. Guess the installer was having a bad day.